Category 3 Hurricane Earl pounding northern Lesser Antilles and Puerto Rico

By: Dr. Jeff Masters , 2:40 PM GMT on August 30, 2010

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An intensifying Hurricane Earl is pounding Puerto Rico and northern Lesser Antilles Islands with heavy rain and high winds this morning. The eye of Earl passed just north of Anguilla at 9am EDT, and Juliana airport on neighboring St. Martin Island recorded sustained winds of 47 mph, gusting to 68 mph at 8am EDT before going silent. An Air Force Hurricane Hunter aircraft currently in Earl just found a central pressure of 960 mb at 9:42 am EDT. This is a significant drop of 25 mb in 25 hours. Top flight level winds at 10,000 feet seen by the Air Force aircraft were 128 mph. Using the usual rule of thumb that the surface winds are 90% of the 10,000 foot flight level winds gives one surface winds of 115 mph, which is right at the border of Cat 2/ Cat 3 strength. Top winds seen at the surface by the Air Force's SFMR instrument were lower, 104 mph. Recent satellite imagery shows that Earl is not perfectly symmetrical--there is still fewer heavy thunderstorms on the hurricane's north side, suggesting that upper-level northerly winds are bringing 5 - 10 knots of wind shear to the storm.


Figure 1. Radar image of Earl taken at 7am EDT 8/30/10 from the St. Maarten radar. Image credit: Meteorological Service of the Netherlands Antilles and Aruba.

Outlook for the Caribbean islands today
Latest radar animations out of Puerto Rico and St. Marten show that the eye of Earl is on track to pass just to the northeast of the islands of Anguilla, St. Maarten, and The Settlement in the British Virgin Islands today. The periphery of Earl's southern eyewall will probably bring Category 1 hurricane conditions to some of these islands today. NHC is giving its highest odds for hurricane-force winds to Saint Maarten--a 99% chance. These odds are 4% for St. Thomas in the Virgin Islands, and 2% for San Juan, Puerto Rico. The main threat to Puerto Rico will be heavy rains--up to eight inches in isolated areas. Earl's rains, in addition to causing flooding and dangerous landslides, will also help alleviate drought conditions that have affected many of the islands this year.

Intensity forecast for Earl
Wind shear as diagnosed by the latest SHIPS model forecast is nearly non-existent over Earl--just 3 knots--put is probably higher than that, based on the fact that the northern portion of Earl cloud pattern is ragged. Further evidence of this is the fact that Earl's eyewall had a gap in its west side, according to the latest report from the Hurricane Hunters. Ocean temperatures are a near-record 30°C, and very warm waters extend to great depth, resulting in a total ocean heat content highly favorable for rapid intensification. These nearly ideal conditions for intensification should bring Earl to Category 4 strength by Tuesday morning, and Category 5 is not out of the question. Earl should be able to maintain major hurricane status through Thursday, when it will make its closest approach to North Carolina. Sea surface temperatures are very warm, 29°C, along the U.S. East Coast, and wind shear is expected to remain low through Thursday. By Friday, when Earl will be making its closest approach to New England, wind shear will rise to a high 20 - 30 knots and ocean temperatures will plunge to 20°C, resulting in considerable weakening. Earl will still probably be a Category 2 hurricane on Friday, when it could potentially make landfall in Massachusetts or Nova Scotia, Canada.


Figure 2. Swath of surface winds from Earl predicted by the 2am EDT Monday August 30, 2010 run of NOAA's GFDL model. Hurricane force winds (yellow colors, 64 kt and above) are predicted to stay off the coast and tropical storm force winds (light green colors, 34 knots and above) are predicted to stay off the U.S. coast, but affect the coast of Canada. Image credit: Morris Bender, NOAA/GFDL.

Track forecast for Earl
Once Earl passes the Lesser Antilles, steering currents favor a northwesterly course towards North Carolina. History suggests that a storm in Earl's current location has a 25% chance of making landfall on the U.S. East Coast, and Earl's chances of making a U.S. landfall are probably close to that. None of the computer models show Earl hitting the U.S., but the storm will likely come uncomfortably close to North Carolina's Outer Banks and to Massachusetts. The latest set of model runs (2am EDT, or 6Z) project Earl will miss North Carolina by 200 - 300 miles on Thursday, and Massachusetts by a similar distance on Friday. Keep in mind that the average error in a 4 - 5 day NHC forecast is 200 - 300 miles, so the East Coast cannot breathe easily yet. The Outer Banks of North Carolina and Cape Cod, Massachusetts are both at the edge of the cone of uncertainty. NHC is giving Cape Hatteras a 9% chance of receiving hurricane force winds. These odds are 14% for Nantucket, 4% for Boston, and 2% for New York City. The main determinant of whether Earl hits the U.S. or not is a strong trough of low pressure predicted to move off the U.S. East Coast Friday. This trough, if it develops as predicted, should be strong enough to recurve Earl out to sea late in the week, with the storm just missing landfall in the U.S., but possibly making landfall in Nova Scotia, Canada.

Regardless of Earl's exact track, the U.S. East Coast can expect a long period of high waves beginning on Thursday. Significant beach erosion and dangerous rip current will be the rule, due to waves that will reach 10 - 15 feet in offshore waters (Figure 3.)


Figure 3. Wave forecast for 8am Friday, September 3, 2010, as produced by the 8pm EDT August 29 run of NOAA's Wavewatch III model. The model is predicting waves of 4 - 5 meters (13 - 16 feet) in the offshore waters from North Carolina to New Jersey.

Hurricane History for the northern Lesser Antilles
The last Cape Verdes-type hurricane to affect the Barbuda and the surrounding northern Lesser Antilles Islands was Hurricane Debby of 2000, which passed over the islands on August 28 as a Category 1 hurricane. Damage was less than $1 million, and no fatalities were reported. The last hurricane of any kind to pass through the northern Lesser Antilles Islands was Category 4 Hurricane Omar, on October 16, 2008. Omar took an unusual track, moving towards the northeast, and the storm's eyewall missed all of the islands. Omar did $80 million in damage to the Caribbean, mainly on the islands of Antigua, Barbuda, Dominica, the SSS Islands (Saba, St. Eustatius, and St. Maarten), and the U.S. Virgin Islands. No direct deaths were attributed to Omar, and the name Omar was not retired from the 6-year rotating list of hurricane names.

Links to track Earl
Wundermap of the northern Lesser Antilles Islands
Long range radar out of San Juan, Puerto Rico
Visible rapid scan satellite loop

97L
The tropical wave (Invest 97L) now 1000 miles east of the Lesser Antilles Islands has a well-defined surface circulation and enough heavy thunderstorms to be classified as a tropical depression, if it can maintain that state for another six or so hours. Satellite loops show the surface circulation clearly, but also that heavy thunderstorm activity has been slow to build. The storm is experiencing low wind shear of less than 5 knots, and is over warm 29°C waters. The main impediment to development continues to be dry air associated with the Saharan Air Layer (SAL) surrounding the storm. The latest SHIPS model forecast calls for shear to stay in the low range, 5 - 10 knots, through Tuesday, and this should allow 97L to organize into a tropical depression today or Tuesday. NHC is giving 97L a 90% chance of developing into a tropical depression by Wednesday.

97L is moving quickly to the west, at about 20 mph. This means it is catching up to Earl, which has slowed down to 14 mph. By Tuesday night, Earl is expected to be a large and powerful major hurricane with a well-developed upper-level outflow channel heading clockwise out from Earl's center at high altitudes. These strong upper-level winds will bring high levels of wind shear, 20 - 30 knots, to 97L, and probably arrest the storm's development. The most likely scenario depicted in the computer models is for 97L to be drawn into the low pressure wake of Earl and pass to the northeast of the Lesser Antilles. Earl would then eventually destroy 97L through high wind shear, and by robbing the storm of its moisture. An alternative scenario is that 97L will stay far enough away from Earl that it will be able to pass through the northern Lesser Antilles islands as a tropical storm on Wednesday and Thursday, then bend northwestwards to potentially threaten the Bahamas and U.S. East Coast. There is a very high degree of uncertainty on what may happen to 97L. History suggests that a storm in 97L's current location has a 25% chance of making landfall on the U.S. East Coast.


Figure 4. Morning satellite image of 97L.

Danielle
Hurricane Danielle is on its way to oblivion over the cold North Atlantic waters, and is only of concern to shipping interests.

Elsewhere in the Tropics
Over in the Western Pacific, tropical cyclone activity is ramping up, with two named storms expected to affect land this week. As is typical in a La Niña year, these storms have developed close to mainland Asia, and don't have a lot of time over water to intensify into strong typhoons. The storm of most concern is Typhoon Kompasu, which is expected to hit Okinawa today and recurve northward into Korea on Thursday. It now appears the Kompasu will not have major impacts on China's largest city, Shanghai. In the South China Sea, the fearsome sounding Tropical Storm Lionrock is forecast to hit the Chinese coast near Hong Kong on Tuesday, but is not predicted to develop into a typhoon.

The GFS model is predicting formation of a tropical depression off the coast of Africa about seven days from now.

Jeff Masters

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Quoting yonzabam:


Earl was due east of PR earlier today and is now NE of it. That's a NW movement.


wnw actually...And pretty much in line with guidance for now. Granted, he is remaining on the southern edge of guidance. He's done that for quite a while now...But again, he is still staying within guidance and the cone.
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That satellite imagery of the three storms is chilling! still can't get over the name Lionrock though :D
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Quoting StormW:
Here are going to be 2 key factors over the next 12-24 hours with Earl:

1.) IF that ridge over the eastern U.S. shifts east or NE.




If the CONUS ridge shifts east or NE, that would mean the CONUS trough's arrival will likely be delayed (based on the forecasted tilt of the trough thru 48 hours) and Earl will push hard up against and around the periphery of the high, and likely moving further westwards.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
1178. unf97
Earl is becoming a monster down there. It would not surprise me at all if he becomes a category 5 hurricane.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
Quoting CoopNTexas:
12z EURO sends 97L/Fiona out to sea



thats the 00Z
Member Since: March 10, 2010 Posts: 1 Comments: 7726
1174. srada
Until today, Our local NWS has been very good on their discussions but now of all times, they dont do an update since 3am this morning and a doomsday storm might be in our forecast for the later period..I wonder due to the uncertainity of Earl's track that they dont want to put out forecasts until NHC does so?

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
AS OF 3 AM MONDAY...FULL SUNSHINE AND ABOVE NORMAL TEMPERATURES
EXPECTED THROUGH THE PERIOD AS HIGH PRESSURE BUILDS BOTH SURFACE AND
ALOFT FROM POINTS NORTH. TUESDAY SHOULD FEATURE A LARGELY PINNED SEA
BREEZE AND 90 DEGREE READINGS SHOULD EASILY MAKE IT TO THE NC COAST
AND PROBABLY EVEN THE GRAND STRAND. SURFACE AND MID LEVEL RIDGE OVER
THE EASTERN U.S. WEAKEN IN FAVOR OF THE WEST ATLANTIC HIGH ON
TUESDAY. THIS WILL ALLOW FOR BETTER AND QUICKER INLAND PENETRATION
OF SEABREEZE AND COAST SHOULD STAY CAPPED IN THE 80S AS INLAND ZONES
ONCE AGAIN WARM INTO THE 90S. FORECAST SOUNDINGS IMPLY A NEAR
CLOUDLESS SKY ON TUESDAY. BY WEDNESDAY THERE MAY BE JUST ENOUGH
SATURATION AT THE CCL FOR A FEW FLAT CU AT ABOUT 5KFT ESP ALONG
SEABREEZE.

DEPENDING HEAVILY ON THE TRACK AND SIZE OF EARL SOME CLOUD COVER
COULD SPREAD OVER EASTERN ZONES LATE WEDNESDAY NIGHT. THE TRACK
BRINGS THE STORM WITHIN ABOUT 330 MILES OF THE COAST. THIS IS ABOUT
THE RADIUS OF CIRRUS ENVELOPE ON THE WEST SIDE OF THE STORM DURING
SOME OF THE BETTER OUTFLOW SURGES.

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Quoting GeoffreyWPB:


Do people even read the NHC Discussions anymore?

EARL IS EXPECTED TO TURN TOWARD
THE NORTHWEST WITHIN THE NEXT DAY OR SO AS IT MOVES AROUND THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE DURING THE NEXT COUPLE OF
DAYS.


Problem is they have been saying that for several days now. They are redefining the term "so" as we speak
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what does it mean for the ridge to "nose" on top of earl
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Quoting tropicfreak:


Thats what they keep saying, but no real consistent NW movement has been occuring.


Earl was due east of PR earlier today and is now NE of it. That's a NW movement.
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Quoting seflagamma:
Are you kidding me.

Had on TWC, we have a major hurricane bearning down on the Islands and on the USVI and PR and TWC is showing a "Storm Stories" movie....nothing coverning this major hurricane.

I expected some coverage about this storm..



You seem to under the impression that The Weather Channel is a weather channel. It's a common error.
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Quoting TampaSpin:


YOu are so right about that. WELL get ready! Things are changing next week as a more ZONAL flow will be coming....Our typical Summer Pattern of the normal SeaBreeze late evening storms and everything will be coming next week.....Big high will develop near Bermuda and NO , NO trough protection for a while it appears. The real ride is coming it appears.


Buckling seat belt now. Gulp!
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1164. xcool
97L OUTT SEA
Member Since: September 26, 2009 Posts: 2 Comments: 15672
12z EURO sends 97L/Fiona out to sea

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1162. Engine2
Quoting kmanislander:


The eye is clearing out rapidly. Don't even think about that ridge nosing over the top of him. That would not be good.

Is the thinking if the ridge nosed over top of him that he would be trapped on a westerly course?
Member Since: February 27, 2006 Posts: 0 Comments: 482
ECMWF now showing a Category 4/5 Hurricane heading towards New York (Earl)

Not wishcasting, just telling what it shows.
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i think Earl is a CAT 4 monster with at 135mph winds right now

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1159. trey33
Quoting DestinJeff:


Is the euro saying that Earl is sucking some of the energy out of 97L? Or am I reading it wrong?
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Quoting msmama51:


thanks. No weather systems (troughs, fronts, etc.)to steer it around?


Follow StormW. His focus is on Earl right now, but 97L or Fiona he will talk about later
Member Since: July 14, 2008 Posts: 1 Comments: 9630
Quoting TampaSpin:


Only the models that show a weak 97L


Check these out......if a stronger 97L

GFS BAMD NGPS CMC
MODELS



First time I saw that. That's a big change. Thanks Tim.
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Quoting StormW:
Here are going to be 2 key factors over the next 12-24 hours with Earl:

1.) IF that ridge over the eastern U.S. shifts east or NE.

2.) He's forecast to become a CAT 4...145 MPH...don't know if he can pump the ridge (modify his environment to create some slight ridging ahead of him to his north).


The eye is clearing out rapidly. Don't even think about that ridge nosing over the top of him. That would not be good.

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Quoting katrinakat5:
kman if the turn happens in 6 hours i agree with you sou fla and the east coast is off the hook...i see no way that will happen though and earl will continue on a wnw to west course and threaten the bahmas with cat 5 winds then sou fla...the cone will continue to shift west bound like its been doing since yesterday...


the scary thing is i am starting to think you may be right but then again if i read something enough times maybe im just starting to believe it
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Quoting RitaEvac:
Explanation:

its moving westward rapidly, which indicates its not gonna turn. Cyclonic flow above Earl has a steering pattern to keep it going west when Earl moves north, by then it's in the Carribbean somewhere, and a building ridge setting up over the east coast after a trough moves out points to Gulf bound


thanks. No weather systems (troughs, fronts, etc.)to steer it around?
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Quoting divdog:
omg such drama

This is "The" drama blog! LOL
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Quoting CybrTeddy:
An impressive beast.


he looks so far N in that one (from pr)
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Quoting hurricaneman123:
does any one think Earl is a CAT 4 monster right now?


I do :)
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Quoting GeoffreyWPB:


Do people even read the NHC Discussions anymore?

EARL IS EXPECTED TO TURN TOWARD
THE NORTHWEST WITHIN THE NEXT DAY OR SO AS IT MOVES AROUND THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE DURING THE NEXT COUPLE OF
DAYS.


Thats what they keep saying, but no real consistent NW movement has been occuring.
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Quoting HadesGodWyvern:


Lionrock (left side of photo)
Namtheun (center of photo)
Kompasu (right side of photo)
I just hope that they all don't hit the same place.
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Quoting StormFreakyisher:
Um its now a major hurricane in the Herbert Box but it is still not headed towards Florida.


My understanding is that the box is not exactly a forecasting tool, but more of a rear view thing. Looking at major hurricanes landfalling in South Florida, you will find that 9 out of 10 of them had passed through the box(es) before landfall.

That does NOT mean that 9 out of 10 major hurricanes that pass through the box will landfall as majors on South Florida. If it did, there would be a whole lot more action in South Florida than there is in terms of boarding up and such.
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1146. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15672
1145. kwgirl
Quoting aspectre:
HurricaneEarl's heading had turned []ward to degrees [] of WestNorthWest
from its previous heading of []
H.Earl's average speed moving between its last 2 reported positions was 11mph(~16.6km/h)

29Aug . 06pmGMT - - 17.4n58.9w - - 75mph - - - 978mb - - NHC.Adv.#17A
29Aug . 09pmGMT - - 17.6n59.5w - - 85mph - - - 978mb - - #18
30Aug . 12amGMT - - 17.7n60.3w - - 85mph - - - 972mb - - #18A
30Aug . 03amGMT - - 17.9n61.1w - 100mph - - - 971mb - - #19
30Aug . 06amGMT - - 18.1n61.8w - 100mph - - - 969mb - - #19A
30Aug . 09amGMT - - 18.3n62.4w - 105mph - - - 969mb - - #20
30Aug . 12pmGMT - - 18.4n62.9w - 110mph - - - 965mb - - #20A
H.Earl becomes Cat.3
30Aug . 03pmGMT - - 18.7n63.6w - 120mph - - - 960mb - - #21
30Aug . 06pmGMT - - 19.0n64.0w - 125mph - - - 955mb - - #21A

Copy&paste 17.4n58.9w, 17.6n59.5w, 17.7n60.3w, 17.9n61.1w, 18.1n61.8w-18.3n62.4w, 18.3n62.4w-18.4n62.9w, 18.4n62.9w-18.7n63.6w, 18.7n63.6w-19.0n64.0w, ngd, gdt, myg, pbi, 19.0n64.0w-30.04n81.3w into the GreatCircleMapper for a look at the last 12hours.

H.Earl's center had made a close passage north of or had hit northernAnguilla.
Using straightline projection upon the speed&heading averaged
over the 3hours spanning the last two reported positions:
~5days from now to Jacksonville.
PERFECT! My Boss just went to Jacksonville on vacation.
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We will not have a good picture of exactly where Earl may be headed towards the East Coast of the US until a few days from now but this potential track is consistent with a few higher trajectories associated with a La Nina year:

Smith, Shawn R., Justin Brolley, James J. O’Brien, Carissa A. Tartaglione, 2007: ENSO’s Impact on Regional U.S. Hurricane Activity. J. Climate,

East Coast landfalling hurricanes, except those forming during a warm phase, typically form farther east than those that strike Florida or the Gulf Coast (Figs. 5–7). In fact, the median longitude of tropical storm classification during cold and neutral ENSO phases is near or less than the 25th percentile longitude for both Florida and Gulf Coast landfalling hurricanes (Fig. 7). Tropical cyclones that form in the far eastern Atlantic have more time to be influenced by upper-level troughs as they travel across the Atlantic, thereby increasing the likelihood that they will reach a more northern latitude and impact the East Coast.

This compares to seven landfalls for every 10 ENSO cold phases along the East Coast. Differences in ENSO cold versus neutral landfall probabilities are notably smaller for Florida and the Gulf Coast (Figs. 2b,c). These results suggest that there is a significant change in formation location and/or steering patterns during neutral years that limits East Coast landfalls.


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One thing is clear we have a bigger eye on EARL.

And the track is in the same line as NHC forecast.
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An impressive beast.
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144 hrs...12z EURO

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Quoting katrinakat5:
earl is mving due west and has been for the last hour now...


Do people even read the NHC Discussions anymore?

EARL IS EXPECTED TO TURN TOWARD
THE NORTHWEST WITHIN THE NEXT DAY OR SO AS IT MOVES AROUND THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE DURING THE NEXT COUPLE OF
DAYS.
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Quoting divdog:
omg such drama


Are you kidding me, that is the name of the game on this blog most times.
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1137. katroy
Quoting spartankicker:


There isn't a site out there that I'm aware of that lists that.

However, ImpactWeather had a presentation at the latest hurricane conference on their rating scale, which shows how to estimate the radius of 100 kt winds (winds at this point begin destructive damage to residences). Just open the pdf at that link. You'll need a calculator to figure it out.


Thanks for the reply, Sparty. The WeatherImpact HSI is exactly what I'm trying to calculate. My interpretation of the paper you referenced is that this is the formula they used to standardize the data used to create the scale used to come up with the HSI for new storms. But it's a pretty complicated paper, so I very well could be missing something.

I was just hoping there was a site that posted a more granular breakdown of the size of the various wind fields of current storms. I'll keep looking!
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1136. HadesGodWyvern (Mod)


Lionrock (left side of photo)
Namtheun (center of photo)
Kompasu (right side of photo)
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1135. Engine2
Storm, you have been quiet. Any comment on the orientation of the trough that's suppose to turn Earl away from New England?
Member Since: February 27, 2006 Posts: 0 Comments: 482
1134. divdog
Quoting serialteg:

omg such drama
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Slow down in forward speed??? ( per appearances on long range San Juan radar)
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Quoting StormW:
Hey kman;nash! Good to see you guys!


Hi Storm. Busy times now and likely to stay that way for a long time.

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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